Multiple Choice
The sodium-potassium pump works by doing what?
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9. Transport Across Membranes
Transporters
Multiple Choice
In eukaryotic cells, how does pyruvate produced by glycolysis enter the mitochondrial matrix for oxidation by the pyruvate dehydrogenase complex?
A
It diffuses freely across the inner mitochondrial membrane because pyruvate is nonpolar at physiological pH.
B
It is imported through the outer and inner mitochondrial membranes via the TOM and TIM protein translocases.
C
It enters the matrix through the voltage-dependent anion channel (VDAC) in the outer membrane, which also spans the inner membrane.
D
It is transported across the inner mitochondrial membrane by the mitochondrial pyruvate carrier (MPC), a specific pyruvate/H+ symporter.
Verified step by step guidance1
Understand that pyruvate is produced in the cytosol during glycolysis and must enter the mitochondrial matrix for further oxidation by the pyruvate dehydrogenase complex.
Recognize that the mitochondrial outer membrane is relatively permeable to small molecules like pyruvate due to the presence of channels such as the voltage-dependent anion channel (VDAC), allowing pyruvate to pass into the intermembrane space.
Note that the inner mitochondrial membrane is highly selective and impermeable to most molecules, requiring specific transport mechanisms for pyruvate to enter the matrix.
Identify that pyruvate crosses the inner mitochondrial membrane via the mitochondrial pyruvate carrier (MPC), which functions as a pyruvate/H+ symporter, coupling pyruvate transport with proton movement.
Conclude that this specific transport system ensures efficient and regulated entry of pyruvate into the mitochondrial matrix where it undergoes oxidative decarboxylation by the pyruvate dehydrogenase complex.
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